From the history available , it seems that you have a long standing inflammatory condition with a swollen appearance and persistent pain in your left armpit.

The most probable cause presenting in this pattern include chronic lymphadenitis due to chronic infections like Tuberculosis, or fungal infections which can be diagnosed by skin testing, and tissue analysis.

In case lymph node involvement has been ruled out by your treating doctor, the other conditions that present in this pattern, include Cellulitis, infections of the hair follicle or sweat glands which form abscesses or boils, Sebaceous cysts, etc. which need treatment with antibiotics and minor surgical procedures (excision or I & D).

Presence of redness, warmth and pain on touch or pressure on the area appearing to be a swelling could be due to cellulitis which may benefit by a course of antibiotics and anti inflammatory medications.

The other possible conditions include abnormal deposits of fat or connective tissue which forming lipomas, or multiloculated cysts, etc. which are benign in nature.

You may consider consulting a dermatologist who after a complete physical examination of the affected site, might consider performing additional tests including a repeat ultrasound, MRI or skin Biopsy which will definitely help to know the underlying issue.

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